Shift click-select, not selecting

What is going with shift-click select, to select from start of a section to end (or vice versa). Many times it does not select that in the middle…
Is it to do with rests…?

Is one of your selections a multi-bar rest? If so, Shift-click won’t work.

EDIT: the reason is that Dorico doesn’t think of the multi-bar rest as an “object” per se.

EDIT 2: found it. Shift-clicking system track selection with a multibar - Dorico - Steinberg Forums

Sorry, was unclear; in most cases there are no multirests, there may be rests pr beats (1/4 rest, 1/8 rest ets, within one or more consecutive bars)

Are you making a selection that crosses instrument changes, or that crosses divisi changes? If you have a reproducible case, please attach the project here so we can take a look.

Are you in Engrave Mode, possibly?

In Write Mode.

It seems to only happens when first selecting a rest (regular rests within bars).